Thermophilic bacteria have received considerable attention as sources of highly active and thermostable enzymes. Recently, the most extremely thermophilic organotrophic eubacteria presently known have been isolated and characterized. These bacteria, which belong to the genus thermotoga, are fermentative microorganisms metabolizing a variety of carbohydrates (Huber, R. and Stetter, K. O., in Ballows, et al., (Ed.), The Procaryotes, 2nd Ed., Springer-Verlaz, New York, pgs. 3809-3819 (1992)).
In Huber et al., 1986, Arch. Microbiol. 144:324-333, the isolation of the bacterium Thermotoga maritima is described. T. maritima is a eubacterium that is strictly anaerobic, rod-shaped, fermentative, hyperthermophilic, and grows between 55.degree. C. and 90.degree. C., with an optimum growth temperature of about 80.degree. C. This eubacterium has been isolated from geothermally heated sea floors in Italy and the Azores. T. maritima cells have a sheath-like structure and monotrichous flagellation. T. maritima is classified in the eubacterium kingdom by virtue of having murein and fatty acid-containing lipids, diphtheria-toxin-resistant elongation factor 2, an RNA polymerase subunit pattern, and sensitivity to antibiotics.
Since, to date, most organisms identified from the archaeal domain are thermophiles or hyperthermophiles, archaea are also considered a fertile source of thermophilic enzymes.